Clinical studies related to cardiac pacing have shown that an optimal atrio-ventricular pacing delay (e.g., AV delay or PV delay) and/or an optimal interventricular pacing delay (e.g., VV delay) can improve cardiac performance. However, such optimal delays depend on a variety of factors that may vary over time. Thus, what is “optimal” may vary over time. An optimization of AV/PV pacing delay and/or W pacing delay may occur at implantation and sometimes, a re-optimization may occur during a follow-up consultation. While such optimizations are beneficial, the benefits may not be long lasting due to changes in various factors related to device and/or cardiac function. The patent applications cited above set forth various improved systems and methods for, inter alia, allowing a pacemaker or ICD to determine and/or adjust AV/PV/VV pacing delays so as to help maintain the pacing delays at optimal values. In particular, techniques were set forth for exploiting various interventricular conduction delays to determine optimal AV/PV/VV pacing delays. Techniques were also set forth for exploiting the VV delays to determine which ventricles should be paced—the left ventricle (LV), the right ventricle (RV), both ventricles, or neither. These various techniques are also described herein below.
Other techniques have been set forth for determining AV/PV delays based on inter-atrial conduction delays and interventricular conduction delays. In particular, see U.S. Pat. No. 7,248,925, to Bruhns et al., entitled “System and Method for Determining Optimal Atrioventricular Delay based on Intrinsic Conduction Delays,” which is fully incorporated by reference herein.
Within certain patients with long inter-atrial conduction delays, circumstances can arise where optimal AV/PV pacing delays are suggested that are longer than the intrinsic AR/PR conduction delays within the patient. This can occur, e.g., within heart failure patients having otherwise normal AR/PR delays (i.e. AR/PR delays of about 150 milliseconds (ms)). As can be appreciated, if the AV/PV pacing delays are set longer than the AR/PR conduction delays, the ventricles might depolarize only in response to atrio-ventricular conduction and hence the V-pulses will not capture. Improvements are set forth herein that address these concerns.